1. Field of the Invention
The present invention relates to an ink-jet recording apparatus comprising a pump that sucks liquid therein and discharges the liquid thereout, to a method for controlling the ink-jet recording apparatus, and to a method for controlling the pump.
2. Description of Related Art
An ink-jet recording apparatus such as ink-jet printers comprises an ink-jet head formed with a large number of nozzles through which ink is ejected. The ink-jet head is connected, through a tube or the like, with an ink cartridge that serves as an ink supply source. During a printing operation, the ink-jet head sucks ink from the ink cartridge by making use of a capillary effect within the nozzles and a difference between the ink cartridge and the nozzles in pressure acting thereon. Then, the ink is ejected through the nozzles, so that an image is recorded onto a record medium such as papers.
However, air bubbles sometimes arise in the tube while, e.g., renewing the ink cartridge. When these air bubbles stay within the tube, suction of ink from the ink cartridge into the head becomes troublesome, which may adversely affect a recording onto a record medium.
As a means for solving the aforementioned problem, known is a technique in which a pump having two tubes passing therethrough is disposed between a head and an ink cartridge and the pump performs a purge operation using one of the two tubes (see Japanese Patent Publication No. 7-80304). The purge operation allows ink containing air bubbles to be discharged, through the nozzles, out of the tube or out of an ink passage of the head.
In this technique, the pump includes a housing in which a cylindrical cavity is formed, and a rotor rotatably mounted within the cavity. Three rollers are rotatably journaled to the rotor. These three rollers are disposed apart by the same angle from one another in a circumferential direction. A diameter of the rotor is smaller than a diameter of the cylindrical cavity in the housing, thus forming a space between the rotor and an inner wall of the housing. The two tubes are disposed through upper and lower portions of this space. The upper tube, which connects the head with the ink cartridge, constitutes an ink supply path. The lower tube, which connects a waste ink tank with a purge cap for covering a nozzle face of the head, constitutes an ink discharge path. The lower tube contributes to the purge operation.